A small-ish SEP spacecraft should be able to do the mission in less than 200 days as well if it got to start at EML2. At 100 days and 1 mm/s acceleration it could get in about 8600 m/s delta-v, and the parts that take delta-v in the chemical mission after leaving Earth's gravity well is all stuff that would get no Oberth benefit whatsoever.

Logged

For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v. Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

I think that we're kind of putting the cart before the horse at this point.

While it would be great to send a probe to this object, it's probably be best if we get better images and radar pictures of this thing to determine if we WANT to spend billions to send a probe or ARM mission to it in the first place.

For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v. Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

The OP was asking about THIS object, and since we haven't had a spacecraft near it, there's nothing for it to perturb gravitationally to get a mass. What you'd do is figure a few 1000 kg/m^3 density, give a factor of 2 uncertainty (mostly on the low side in case it's like Mathilde). Given the uncertainty in the size, there's probably about a factor of 10 uncertainty in mass right now. I suspect the size can be measured pretty accurately by radar from the intensity of a reflected signal.

Given that Congress seems to want to kill ARRM, it would probably be more useful to think of a low-cost way to get a probe to the asteroid. The Japanese Procyon would likely be a good departure point for a design, but of course its SEP failure would have to be diagnosed and remedied.

The OP was asking about THIS object, and since we haven't had a spacecraft near it, there's nothing for it to perturb gravitationally to get a mass. What you'd do is figure a few 1000 kg/m^3 density, give a factor of 2 uncertainty (mostly on the low side in case it's like Mathilde). Given the uncertainty in the size, there's probably about a factor of 10 uncertainty in mass right now. I suspect the size can be measured pretty accurately by radar from the intensity of a reflected signal.

Given that Congress seems to want to kill ARRM, it would probably be more useful to think of a low-cost way to get a probe to the asteroid. The Japanese Procyon would likely be a good departure point for a design, but of course its SEP failure would have to be diagnosed and remedied.

The OP was asking about THIS object, and since we haven't had a spacecraft near it, there's nothing for it to perturb gravitationally to get a mass. What you'd do is figure a few 1000 kg/m^3 density, give a factor of 2 uncertainty (mostly on the low side in case it's like Mathilde). Given the uncertainty in the size, there's probably about a factor of 10 uncertainty in mass right now. I suspect the size can be measured pretty accurately by radar from the intensity of a reflected signal.

If the orbit is known, the mass is known.

- Ed Kyle

How? The moons of the outer planets were used to find the planets' masses using Kepler's third law. It's a standard introductory astronomy exercise. Knowing the orbit of an object around the Sun, for example, can tell you the mass of the Sun, but not the object itself, unless the mass of the smaller object is great enough to cause a measurable reflex motion of the Sun. The mass of this tiny rock is utterly insignificant compared to the mass of the Sun.

That article specifically EXCLUDES 2016 HO3.It does not have a satellite from which to calculate the mass.It is WAY too small to perturb the orbits of any other body.No probe has flown by it to be deflected by its gravity.

Extended observation of the orbit can bound the non-Keplarian nature, that is, how solar wind and light pressures affect the orbit. That can yield an approximation of density, or "ballistic coefficient", kg/m^2.If one then has the size, one can estimate the mass.But..

All the evidence for size is the brightness, distance, distance to the sun, and an assumed albedo. (reflectivity)One can use the albedo measured for known asteroids, but the resulting values say that 2016 HO3 is not like previously observed asteroids.

NHATS says that it is too far for radar measurements.It's too faint for most spectral measurements. It is too faint to measure by observing a stellar occultation, which is unlikely in any case.

It's not clear how much we can learn about it without going there.

No one will plan a crewed mission without SOME reconnaissance before hand.Getting a reconnaissance mission approved and funded is a big challenge, as are all proposed missions.

A dot. Resolution of Hubble at that distance should be 5 km for violet/soft UV wavelengths.

What sort of image could we expect from JWST of this object?

JWST is bigger, but it's also restricted to longer wavelengths so its maximum resolution should still be >4 km. You'd need a diffraction limited telescope with a 100m main mirror (or an interferometer with a baseline of that magnitude) to resolve this asteroid. For pretty pictures, sending something close to it is the only real option.

Communication requirements for a spacecraft should be pretty lenient though. It shouldn't need a dedicated DSN dish. A mission to it could be great for a new laser communications tech demonstrator since the distance is significantly larger than Earth-Moon but well smaller than Earth-Mars.

For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v. Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Dawn is a likely spacecraft of which a copy would be appropriate for a mission to 2016 HO3. It was capable of ~10 km/sec delta V, and had a visible "framing" camera, a visible and near IR spectrometer, and the Gamma Ray and Neutron Detector (GRaND). It cost about a half billion dollars a decade ago.

OSIRIS-REx is another. It includes even more instrumentation and TAGSAM, the Touch and Go Sample Acquisition Mechanism. However it doesn't have much propulsion and is costing about one billion dollars.

Such a mission would have to compete with other Discovery or New Frontiers class planetary missions, of which there are several.

It doesn't seem appropriate for laser communications because there just wouldn't be that much data to send back. Mapping the surface at 1 cm resolution would take ~1GB.

« Last Edit: 06/18/2016 08:16 PM by Comga »

Logged

What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

It's really faint.Which telescopes could observe 2016 HO3 in the thermal infrared?WISE is no longer doing thermal infrared observations, and it is not clear that 2016 HO3 ever went across WISE's line of sight, given the odd orbit, or that it could be seen by WISE. (Wise expanded the population of <1km NEOs, but how many <0.1 km NEOs did it find?)Does it get far enough from the Sun to allow JWST to look at it, when JWST launches and IF observing 2016 HO3 successfully competed for observing time?

« Last Edit: 06/18/2016 08:18 PM by Comga »

Logged

What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

It's really faint.Which telescopes could observe 2016 HO3 in the thermal infrared?WISE is no longer doing thermal infrared observations, and it is not clear that 2016 HO3 ever went across WISE's line of sight, given the odd orbit, or that it could be seen by WISE. (Wise expanded the population of <1km NEOs, but how many <0.1 km NEOs did it find?)Does it get far enough from the Sun to allow JWST to look at it, when JWST launches and IF observing 2016 HO3 successfully competed for observing time?

Duration should be reasonably short, distance for communicating back is fairly low. No issue with distance from the Sun for solar panels. Flyby would give useful info, and might not have to be at huge speed (depending on SC lifetime).

Duration should be reasonably short, distance for communicating back is fairly low. No issue with distance from the Sun for solar panels. Flyby would give useful info, and might not have to be at huge speed (depending on SC lifetime).

Cheers, Martin

A big problem is propulsionIt is safe to assume that the delta-V in the NHATS models is equally distributed among the three.That means the flyby needs ~2.5 km/sec.That's a lot of propulsionCubesats rarely have any, and none have had 1% of this. And you know the tyranny of the rocket equation.And no cubesats have had high Isp SEP.

Logged

What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

A dot. Resolution of Hubble at that distance should be 5 km for violet/soft UV wavelengths.

What sort of image could we expect from JWST of this object?

JWST is bigger, but it's also restricted to longer wavelengths so its maximum resolution should still be >4 km. You'd need a diffraction limited telescope with a 100m main mirror (or an interferometer with a baseline of that magnitude) to resolve this asteroid. For pretty pictures, sending something close to it is the only real option....

Chris Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0